The worst driving stereotypes have long been divided like a highway: women are ditzy and men are risky. But women are taking more risks than they used to on the road, at least when it comes to drinking and driving.

Researchers recently gathered in Washington, D.C., to present data on the female drunk-driving “epidemic” in an attempt to better understand why more women are getting boozy and slipping behind the wheel.

The academics and advocates at the Transportation Research Board’s annual conference presented sobering statistics on the growing trend, though they also acknowledged that the data is sparse. A report from the Traffic Injury Research Foundation lays some groundwork: DWI arrests for women have been climbing, almost 30% from 1998 to 2007, and the proportion of male-to-female arrests has been decreasing. A rise in binge drinking among women in the U.S. may be fueling the trend. And female drivers now outnumber male drivers in the U.S. by 2 million, which helps build a perfect storm of conditions that makes it likely that more women will drink and drive.

Drunk driving is one of many habits — like smoking or bungee jumping or sleeping around — that falls into a broader category of risk-taking behavior. Although studies have shown that women are more risk-averse than men, McGill University’s Thomas Brown, who called female drunk driving an epidemic, argued that some women may have the same cognitive problems with “executive control” that have typically been associated with risk-taking, DWI-prone men. Executive control is a blanket neurological term for the way we plan and make choices. Problems related to such impaired control include poor memory, failing to learn from past experiences or motor impulsivity, a clinical way of saying “acting before thinking.”

But while women could be drinking more because they’re throwing caution out the window, there may also be more insidious social forces at work, like female-directed marketing campaigns for alcohol.

Then there are the traditional drives that make drinking so appealing, including stress, anxiety and, especially among young people, a desire to fit in socially. Brown says women who repeatedly drink and drive are often “wrapped up with psychosocial dysfunction” in which drinking becomes a response to anxiety or job problems.

Researchers at the meeting pointed to characteristics common among female drunk drivers. Jane Maxwell, a substance-abuse expert from the University of Texas at Austin, surveyed women who were in Texas public treatment programs and had been arrested for driving while intoxicated within the past year. Compared with similar men, she found the women were more likely to be unmarried and have less steady employment. They were also more likely to have a primary problem with drugs like cocaine, as well as a diagnosis of depression or bipolar disorder.

The head of the Traffic Injury Research Foundation, Robyn Robertson, also delved into some of the factors that link female drunk-driving offenders. Her organization hosted focus groups with more than 150 women, ranging in age from their late teens to mid-60s, who had been arrested for drunk driving, some for the first time and others for the seventh time. Among them, certain trends stood out: young women who were drinking because other people were; newly married mothers who started drinking after the birth of their children; and empty nesters, who may be trying to escape the stress of a divorce or a parental illness.

Still, despite the recent increase in women drinking (and driving), more men drive drunk. But that might change if the trends continue, Brown cautions. Advocacy campaigns appear to be working to reduce drunk driving among men but not among women, he says, and the biggest hurdle to changing that is the lack of information. “We’re really in the early days,” he says, of understanding the unique factors that compel women to drink and drive. “Women need to be researched more.” That said, advocates do have some dissuading statistics at hand. At the meeting, for example, Maxwell advocated a campaign that would alert women to the link between binge drinking and STDs, which could certainly be a step in the right direction.